Use of wireless networks, such as wireless local area networks (WLANs) is becoming widespread. Locating wireless units, such as radios, in a wireless communication system, such as a WLAN enables new and enhanced features, such as location-based services and location-aware management. For example, location based services can be used for assigning the correct closest printer to a wireless unit of a WLAN.
One technique employed for locating wireless units is time difference of arrival (TDOA). TDOA determines the location of a wireless unit based on the time of arrival (TOA) of a signal sent by the wireless clients. For example, the TOAs at N+1 receivers can be employed to locate a wireless unit in N dimensional space. Thus, higher resolution of TOA measurements from the receivers can result in higher accuracy in determining the location of the wireless unit. However, there are factors which can impact the resolution of a TOA measurement at a receiver. For example, the sampling rate of the receiver can affect the accuracy of a TOA measurement. This is because the speed of electromagnetic radiation (e.g. light) is about 1 foot per nanosecond (ft/ns). For example, the resolution of receivers with a sampling rate of 40, 80 and 120 MHz are ±12.5, ±6.25 and ±4.2 ns respectively (in time) or ±12.5, ±6.25 and ±4.2 feet respectively. Multipath is another factor that can impact TOA measurement. In a multipath environment, a receiver may receive a line-of-site (LOS) signal and at least one non-line-of site (NLOS) signals, thus the receiver has to select the correct line of site signal.